Many spraying guns have been used widely for cleaning dust and dirt from a surface of an object, for watering, for spraying paint, and the like. The spraying guns remove dust and dirt by spraying a high pressure fluid, and perform watering and spraying paint with the use of a high pressure fluid mixed with water or other spraying liquid.
In a conventional prior art, a high pressure fluid is introduced into the spraying gun and is then sprayed out from an outer transmission tube of the spraying gun. An inner transmission tube, which has a cross section area smaller than that of the outer transmission tube, is provided in the outer transmission tube. When the high pressure fluid is sprayed out of the outer transmission tube, Venturi effect is induced at an outlet of the inner transmission tube, it makes a spraying liquid be sprayed out from the inner transmission tube.
In order to uniform the spraying distribution, the outer transmission tube of the spraying gun is made to have a bending shape and in rotation when driving. The inner transmission tube disposed in the outer transmission tube is made of a flexible material, so as to be deformed by bending with the rotation of the outer transmission tube. Thus, a mixed fluid of the high pressure fluid and spraying liquid will be spraying uniformly in every direction with the rotation of the outer transmission tube. However, with the increasing time duration in use of the spraying gun, the inner transmission tube may be worn down or broken due to friction to the outer transmission tube, that result in reducing of durability and parts replacement with increasing frequency.